Would be good to have tests in NetworkUtilsTest for 192.168.*.* and 169.254.*.* (looks like those are currently missing).

Also, for `test172_16_x_xSubnetPrivate()` it create `InetAddress.getByAddress(new byte[] { (byte)172, 31, (byte)255, (byte)255 })`. Am I missing something? Why doesn't it use 16 rather than 31 for the second byte? I presume that test still passes for you.